Fluid flow controller and meter

ABSTRACT

A fluid flow controller and meter including a metering tube with a bore formed axially therein having a slit-like orifice axially disposed and intersecting the bore along the length thereof. Flow through the meter is controlled by a valve member which moves in the passage of the metering tube and across the slit-like orifice. In a preferred embodiment, the slit-like orifice is in fluid communication with a site tube which contains a flow sensitive element which is responsive to the flow induced. The slit-like orifice achieves a linear flow response to changes in the relative position of the valve member.

TECHNICAL FIELD

The present invention is broadly related to the field of fluid flow andapparatus for controlling and regulating such flow. More narrowly,however, the invention deals, in a specific embodiment, with thetechnology of controlling and regulating flow of corrosive liquids, suchas various acids, bases and solvents, and deionized water. A preferredembodiment in accordance with the invention employs a metering valvehousing tube having a slit-like orifice for achieving improved linearflow response resolution and repeatability.

BACKGROUND OF THE INVENTION

The regulation and metering of fluid flow is an essential step performedin industry. For example, different caustics and corrosive acids areutilized in the manufacture of various integrated circuit devices. Itcan be particularly important to know quantities of the differentreagents transferred, and consequently, measuring and controlling flowrate accurately can be critical to the quality of a finished product.

To adequately control the metering rate of a particular fluid, a flowmeter must be sensitive to manual rate adjustments. Rate adjustments aregenerally accomplished by altering the percentage opening or incrementalopening of a valve member. It is preferred that the flow rate respond ina predictable and repeatable linear fashion as the manual flowadjustment valve is cycled over the full range of flow to be measured bythe flow meter. It is desirable to have control over extremely smallflow changes for process control and product yield. It is preferred thatfor each incremental opening of the manual valve controlling the fluidflow there is a linear proportional response in flow rate over theentire range of the flow meter. Thus, a full rotation of the valvehandle should give approximately the same change in flow rate whethersuch full turn occurs at low flow rates or high flow rates over designrange of the meter.

Additionally, because of the nature of the chemicals that are employedin industry, apparatus for controlling and metering the flow of suchchemicals must be impervious to deformation and deterioration whichmight occur when the chemicals under pressure come in contact with thecomponents of such systems. The safety hazards inherent in a system notimpervious to deterioration will be apparent.

Accordingly, the need exists for a flow controller and meter which givesa predictable, repeatable, linear flow performance. The flow metershould be designed to give an equal proportional response to flow for anequal change in manual flow control valve position. This equal linearresponse or change in flow rate should be maintained over substantiallythe entire range of flow rates through the meter. Further, the flowmeter should be designed to withstand corrosive and causticenvironments.

The present invention addresses these needs as well as other problemsassociated with existing flow controllers and meters. The presentinvention also offers further advantages over the prior art and solvesproblems associated therewith.

SUMMARY OF THE INVENTION

The present invention is a flow controller and meter which includes ametering tube having a passage formed axially through the body thereof.One end of the passage can function as a discharge aperture of themeter, fluid having passed through the meter exiting through thisaperture. The metering tube is provided with a slit-like orificeintersecting the passage intermediate its axial ends.

The invention further comprises a sight tube or a conduit which has abore formed axially therethrough. The sight tube bore or conduit bore isin fluid communication, through the orifice, when the orifice isunobstructed, with the passage in the metering tube. The conduitincludes means for measuring a volumetric flow of fluid through the flowcontroller and meter. The bore in the sight tube houses a flow sensitiveelement which is disposed for axial movement therealong.

The flow sensitive element is biased toward a position away from theintersection of the sight tube with the metering tube. The size andspatial relationship of the element is such, relative to the bore, sothat, as the element approaches an end of the bore proximate theorifice, an increasingly greater volume of fluid is permitted to passthrough an annular space between the flow sensitive element and the walldefining the bore.

A valve member is disposed in the passage for selective positioningaxially therealong and across the orifice. Fluid flow through the meteris, thereby, regulated by adjusting the positioning of the valve memberthus functioning as a flow controller. As the valve member is adjustedto enlarge or diminish the size of the portion of the orifice throughwhich flow will be permitted, the location of the flow sensitive elementalong the bore will vary. As the valve member is positioned to permitincreased fluid flow through the orifice, the flow sensitive elementwill be urged by the fluid flow toward an end of the bore proximate theorifice giving a relative measurement of flow. Further, means areprovided for ascertaining the level of volumetric flow of fluid throughthe flow meter depending upon the axial location of the flow sensitiveelement at which it stabilizes after flow has been adjusted.

In the preferred embodiment, the orifice is slit-like in shape. Aslit-like orifice is one that is generally rectangular having a lengthsubstantially greater than the width. The slit-like orifice is disposedwith its length axial or generally parallel to the metering tubepassage. A leading edge of the valve member is generally linear anddefines a rectangle with respect to the slit-like orifice as thatleading edge moves across the orifice. It is envisioned that the leadingedge would be generally perpendicular to the axis with respect to whichthe valve member is moved.

As can be seen then, as the orifice is initially uncovered to permitfluid flow, only a very small rectangular area will be exposed. As thevalve member is retracted increased linear distances of the samedimension, however, the volume of flow increase will be approximatelyequal to previous retractions of the same distance due to therectangular shape of exposed orifice. Consequently relatively equalchanges in flow rate can be made with equal adjustment to the positionof the valve member. Further, the width and length of the slit-likeorifice can be varied for each meter to give a desired range of flowrates and sensitivity for various applications.

The sight tube can be provided with a flared bore, the larger diameterof the bore being more closely proximate the intersection of the sighttube with the metering tube. As can be seen then in view of thisdiscussion, when the flow determinant diametrical dimension of the flowsensitive element is maintained constant, as flow is increased throughthe meter in response to a retraction of the valve member to expose agreater portion of the orifice, the flow sensitive element will be urgedin the direction toward the orifice, and a larger annulus area aroundthe flow sensitive element in the sight tube will permit a greatervolumetric flow of fluid through the tube. The attainment of an axialposition by the flow sensitive element at a location more closelyproximate the orifice will, therefore, be representative of a greaterflow rate than will one at a distance farther from the orifice.

The sight tube can be provided with a series of graduated indiciatherealong. Flow can be ascertained by noting the position of the flowsensitive element with respect to the various indicia when flow isadjusted by axially moving the valve member within the metering tube.The meter can be calibrated so that, for any particular sight tube andflow sensitive element combination, the position of the element at aparticular indicium is known to represent a particular volumetric flowvalue.

As one will note in view of this disclosure, the flow sensitive element,necessarily, is not maintained closely proximate the wall defining thebore. As a result, it might be free to divert from a coaxialrelationship relative to the bore, unless steps were taken to maintainit in such a relationship. Inaccurate measuring might, therefore,result.

The invention, however, contemplates the employment of a rod, coaxialwith the bore, which passes through an aperture central within the flowsensitive element. In this manner, the element can be maintained in acoaxial relationship to the bore.

The various components can be formed from materials to make the meterimpervious to deterioration by caustics or acids. For example, themetering tube in one embodiment of the flow sensitive element can beformed from polytetrafluorethylene. Other embodiments of the inventioncan employ flow sensitive elements made either completely of stainlesssteel or some combination of stainless steel and perfluoroalkoxypolytetrafluorethylene, and the sight tube can be made ofperfluoroalkoxy.

The present invention is thus an improved flow controller and meter foruse with fluids, and particularly liquids which readily interactchemically with materials from which flow meters are typically made.Because of the structure of the meter, it provides highly accuratereadings of fluid flow therethrough and a linear response in flow raterelative to the valve member position. More specific features andadvantages obtained in view of those features will become apparent withreference to the DETAILED DESCRIPTION OF THE INVENTION, appended claimsand accompanying drawing figures.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings, in which like reference numerals indicate correspondingparts or elements of preferred embodiments of the present inventionthroughout the several views:

FIG. 1 is a partial sectional view of a flow meter in accordance withpresent invention as mounted to a mounting plate;

FIG. 1a is an enlarged partial sectional view of the valve member in afully closed position illustrating the shutoff sealing surface of apreferred embodiment;

FIG. 1b is a cross sectional view along line 1b--1b of FIG. 1 depictinga preferred orientation of the slit-like orifice relative to the valvemember;

FIG. 2 is a side-sectional view of the sight tube of the flow meter ofFIG. 1;

FIG. 3 is an enlarged side sectional view of the flow sensitive elementof the flow meter FIG. 1;

FIG. 4 is a graph illustrating a number of curves plotting the linearresponse of flow rate change to valve member position of the presentinvention; and

FIG. 5 is an enlarged side sectional view illustrating an alternativesight tube construction.

DETAILED DESCRIPTION OF THE INVENTION

Detailed embodiments of the present invention are disclosed herein.However, it is to be understood that the disclosed embodiments aremerely exemplary of the present invention which may be embodied invarious systems. Therefore, specific details disclosed herein are not tobe interpreted as limiting, but rather as a basis for the claims and asa representative basis for teaching one of skill in the art to variouspractice the invention.

Referring now to the drawings, FIG. 1 illustrates a flow meter 10 inaccordance with the present invention as mounted to a plate or wall 12.The meter 10 includes upper and lower mounting fixtures, the upperfixture extending from a metering tube 18 as will be discussedhereinafter. The lower fixture 16 comprises a portion of an elbow 20 towhich a sight tube 22 is mounted.

Each fixture has a threaded boss 14, 16 which extends through acorresponding aperture 24, 26 in the plate 12 to effect mountingthereto. FIG. 1 shows internally threaded apertures 28, 30 in the bosses14, 16 for receiving corresponding, externally threaded, inlet andoutlet tubing fittings (not shown). Lock nuts 32, 34 are provided on thebosses 14, 16. The tubing fittings can be threaded into the bosses 14,16 and the nuts 32, 34 tightened down. as tightening progressivelyincreases, commensurately increased pressure will be exerted on thetubing ends to securely hold them within the fitting bosses 14, 16.

The operative portions of the meter 10 include a metering tube 18 which,as previously indicated, is, in the preferred embodiment, integrallyformed with the upper fitting by which the meter 10 is secured to themounting plate 12. The metering tube 18, has formed therein, a passagewhich extends generally coaxially with respect to an axis of elongationof the tube 18. The passage includes first, narrowed, and second,radially expanded portions 36, 38, respectively.

A valve member 40 is received within the expanded passage portion 38 forselective movement along the axis of the passage portion 38. Movement isaccomplished by rotating a knob 42 secured to an end of the valve member40 which extends from the metering tube 18 at an end remote from themounting plate 12. Securing of the knurled knob 42 to the valve member40 can be effected by employment of a screw 44, the head of which isreceived within a recess 46 within the knob 42 when the screw 44 istightened down.

A plug 48 having an internally threaded channel 50 formed therein closesthe end of the metering tube 18 remote from the plate 12. The channel 50therein is sized similarly to, and is compatibly threaded with, anexternally-threaded portion 52 of the valve member 40 which extendstherethrough. The plug 48 is tightened down and is maintained inposition to occlude the end of the metering tube 18 remote from themounting plate 12. The axial movement of the valve member 40 along thepassage 38 is effected by threading the member 40 into and out of thepassage 38 relative to the plug 48.

A seal 54 is held in place by the plug 48 to prevent any leakage of thefluid being metered by the flow meter 10. The seal 54 includes aradially expanded portion 56 which defines a shoulder 58, the shoulder58 abuttably engaging an axially facing shoulder 60 internally withinthe passage 38, when the plug 48 is threaded inwardly in the passage 38to close the end thereof. The radially expanded portion 56 of the seal54 has an axial dimension such that, when the plug 48 is completelytightened down, it will be tightly maintained in position with theshoulder 58 of the seal 54 engaging the shoulder 60 defined by the innerwall forming the passage 38.

As seen in FIG. 1, an end of the valve member 40 most closely proximatethe mounting plate 12 has a diameter closely approximating that of thepassage 38 at all locations which can be coextensive therewith. As aresult, the valve member 40 substantially seals the passage 38 andprecludes axial flow therethrough beyond the valve member 40.

The metering tube 18 has an internally threaded aperture 62 approachingtoward the passage 38 from the side of the tube 18. The aperture 62, inturn, communicates fluidly with the passage 38 through a slit-likeorifice 64 which intersects the passage 38 at a location that can becoextensive with an occluding portion 66 of the valve member 40. Becauseof this relationship valve member 40 can preclude fluid communicationthrough the orifice 64 to the passage 38 when the valve member 40 is inposition completely eclipsing the orifice 64.

FIG. 1a illustrates the relationship between the narrowed passage 36,the expanded passage 38 and valve member 40 when the valve member is ina fully closed position completely eclipsing the orifice 64. A shoulder67 which lies generally perpendicular to the axial direction of passage36 is formed at the intersection between the narrow and radiallyexpanded passages 36, 38, respectively. The shoulder 67 provides asecondary sealing surface for valve member 40 when it is desired toassure complete shut off of flow. Unlike many other flow controllerswhich utilize the same surface for controlling orifice size and shutoff, the valve of the present invention provides a different sealingsurface for each. This feature prevents damage to the flow controlsurface when flow is completely stopped. This increases the reliabilityand repeatability of flow control with the present invention.

In one embodiment, a conduit 22 may be used, rather than the sight tube,in fluid communication with the aperture 62. The conduit 62 canincorporate means for measuring the volumetric flow of fluid through thefluid flow controller and meter. This means may include devices known inthe art such as differential pressure measuring devices, venturi metersor a sight tube flow sensitive element arrangement as described below,for a preferred embodiment.

In a preferred embodiment, a sight tube 22 is threadedly mated, by itsupper end, with the aperture 62 that communicates with the passage 38through the orifice 64. A lower end of the sight tube 22 is mated to theelbow 20 comprising the lower fitting.

The sight tube 22 has a bore 68, extending between the opposite ends ofthe tube 22, formed therein. The lower end of the bore 68 communicateswith a 90 degree channel 70 in the elbow 20, and the upper end of thebore 68 communicates, through the orifice 64, with the passage 38 in themetering tube 18. A continuous channel is, thereby, formed. Flow ispermitted through that channel when the valve member 40 is retracted toa point so that at least a portion of the slit-like orifice 64 is notobstructed.

The bore 68 illustrated in FIG. 1 is tapered, and it is shown as havinga diameter greater at its end by which the sight tube 22 is mated to themetering tube 18. A flow sensitive element 72 is disposed in the bore 68for axial movement therealong. Typically, the flow meter 10 would beoriented wherein the axis of elongation of the metering tube 18 isoriented generally horizontally and wherein the axis of elongation thesight tube 22 is oriented generally vertically. It will be understoodthat, when the flow meter 10 is so oriented, the flow sensitive element72 is biased downwardly. In the embodiment illustrated in the figures,the flow sensitive element 72 is biased downwardly by gravity.

It will be understood, however, that other orientations of the flowmeter 10 are contemplated. Biasing would likely, still be employed tobias the flow sensitive element 72 in a direction away from the meteringtube 18, but other methods of biasing would be employed when suchorientations were practiced.

As seen in FIG. 1, the flow determinant diameter 74 of the flowsensitive element, or float 72, is smaller than the internal diameter ofthe bore 68, even though that diameter can be varied from one embodimentof the invention to another, as is illustrated by use of phantom lines,as at 74' in FIG. 3. This is true even when the float 72 is at aposition near the bottom of the bore 68 at a section thereof having thenarrowest internal diameter. In order to maintain the float 72 coaxialwith the bore 68, therefore, a rod 76 can be employed as a guide. Therod 76 would be aligned along the axis of the bore 68 and would passthrough an aperture 78 centrally within the float 72.

The rod 76 can be mounted in a wall 80 of the channel within the elbow20 comprising the lower mounting fixture. The rod 76 would be of alength such that the float 72 could be free to move substantially alongthe full length of the sight tube 22. The rod 76 can be provided, at itsupper end, with a bead 82, larger than the aperture 78, to preclude theflow sensitive element 72 from coming off the rod 76 and preventplugging of the outlet orifice and consequent restriction of fluid flow.

When a flow meter 10 as illustrated in FIG. 1 is secured to a mountingplate 12 for use, the valve member 40 would typically be in a positioncompletely occluding the orifice 64. The inlet and outlet tubes would bemated to their respective bosses 14, 16 after the flow meter 10 weremounted to the plate 12, and the mounting nuts 32, 34 would be tighteneddown. Valves (not shown) in the fluid system could be opened to permitflow of the fluid into the meter 10 at a constant pressure. Meteringcould then be accomplished by manipulating the knurled knob 42 to effectwithdrawal of the valve member 40 within the passage 38 to an initialpoint where at least a portion of the slit-like orifice 64 becameuncovered.

FIG. 1 illustrates a valve member 40 having a planar face 84 mostproximate the mounting plate 12. Consequently, the forward edge of thevalve member 40 functions, with respect to the slit-like orifice 64, todefine a rectangle of varying area. As the valve member 40 is retractedto reveal more of the orifice 64, the rectangle defined by the forwardedge of the valve member 40 will move across the orifice 64 exposingmore and more thereof.

The orifice 64 is slit-like in shape. By slit-like it is meant that theorifice is generally rectangular in shape with the length of the orificesubstantially greater than the width. Because the orifice 64 isgenerally rectangular in shape, as the valve member 40 is retracted toreveal more of the orifice, the area of the orifice 64 exposed to fluidflow varies proportionally with the degree with which the valve member40 is retracted. This results in the beneficial effect of having animproved linear fluid rate change relative to each equal incrementalchange in positioning of valve member 40.

FIG. 1b depicts the relative relationship between valve member 40 andthe slit-like orifice 64. In FIG. 1b the valve member 40 is in partiallyretracted position exposing a portion of the slit-like orifice, arectangular shape, to fluid flow. The covered or occluded portion of theslit-like orifice 64 is shown in phantom as occluded by the valve member40. The slit-like orifice 64 lies coaxially with the valve member 40 ina preferred embodiment.

FIG. 4 illustrates several graphs depicting the linear response of theflow controller and meter of the present invention relative to thepositioning of a valve member 40. The flow rate is given relative to thepercentage opening of the valve member.

As can also be seen in the graphs of FIG. 4, the dimensions of theslit-like orifice 64 can be varied to give different flowcharacteristics over the full range of exposure of the orifice 64. Thewidth may be varied to give a broader overall range of flow rates. Anarrower slit may be utilized to achieve more precise flow measurementover a narrow range of flow rates.

As previously indicated, the bore 68 within the sight tube 22 flaresradially outwardly as the float 72 moves upward within the bore 68.Consequently, the cross-sectional area of the annular space 86surrounding the float 72 through which flow occurs becomes greater asthe float 72 rises within the tube 22. As more flow is induced byretracting the valve member 40 farther within the passage 38, theincreased flow will cause the float 72 to rise so that the flow throughthe bore 68 will seek to approach the flow that would actually beinduced as a result of exposing more of the orifice 64.

As will be able to be seen, then, the position that the float 72 attainsin response to retraction of the valve member 40 by manipulation of thecontrol knob 42 correlates with the actual amount of volumetric flowthrough the meter 10. A particular flow meter can be calibrated so that,for any given slope of the wall defining the bore 68 of the sight tube22, actual flow can be tabulated for any position of the float 72 withinthe tube 22. Graduations 88 can be marked, by scoring the sight tube 22,to indicate a particular flow level. The embodiment illustrated in FIG.1 shows graduations 88 which are equally spaced along the tube 22. Apaper backing (not shown) can be applied to a circumferential portion ofthe sight tube 22 to highlight the location of the float 72 relative tothe graduations 88.

Another factor which bears upon the position that the float 72 willattain in response to retraction of the valve member 40 is the weight ofthe float 72. The float weight can be varied, therefore. If it is madeheavier, greater flow can be ascertained without exceeding the limits ofthe meter 10. Again, a meter 10 having a particular angle of slope ofthe inner wall defining the bore 68 in the sight tube 22, in combinationwith a particular float 72, can be calibrated so that the amount of flowrepresented by the float 72 attaining any particular position is known.

When a flow meter 10 in accordance with the present invention is to beutilized, the purchaser of a unit would have some sense of the rangeswithin which metering would want to be performed. If relatively lowvolumes are to be metered, a flow meter having a narrow slit-likeorifice would probably be the optimum choice. The use of that meterwould obtain greater discrimination capability. If flow is to be meteredover greater ranges, however, meters having a wider slit-like orificewould probably be necessary.

Another variation which the present invention envisions is one whereinthe bore formed in the sight tube 22 is not sloped but, rather, has astepped diameter. At the lower end of the tube 22, the diameter would beuniformly narrow, as at 96, while the diameter would expand into auniformly enlarged segment immediately above, as at 98. The diametersegments would be coaxial with respect to one another. An axiallyupwardly facing shoulder 100 would, thereby, be defined.

In this embodiment, the float 102 would be provided with a conicallytapering wall 104, the wall tapering inwardly as it extends downwardly.The greatest diameter of the float 102 would be at its upper end sothat, when flow is not induced through the meter 10, the upper edge 99of float 102 would be proximate shoulder 100. As flow would be induced,however, through the meter 10, the float 102 would rise within the boreof the sight tube 22. Because of the tapering of the float 102, theannular space 106 between the float 102 and the edge of the shoulder 100defined within the sight tube 22 by the differing diameters of the borewould increase as the float 102 rises.

The size and spatial relationship of the float 102 relative to the borewould be such that, as the float 102 would approach an end of the boreproximate the orifice 64, an increasingly greater volume of fluid flowwould be permitted through the bore around the float 102. Thisembodiment would be particularly desirable when low flow rates aredesired to be regulated.

Another variation which is contemplated would be one wherein the sitetube is downstream of the metering tube. It will be understood that,with regard to this aspect of the invention, positioning of the sitetube upstream of the metering tube is not essential.

Because the flow meter 10 is particularly adapted for use with causticand corrosive chemicals the various components can be made of plasticmaterials to make them impervious to chemical reaction that might resultbecause of contact with the chemicals. For example, it is envisionedthat, in the preferred embodiment, the metering tube 18, the elbowfitting 20, and the float 72, at least in part, be made ofpolytetrafluorethylene. The rod 76 along which the float 72 rides couldbe made of chlorinated tetrafluoroethylene. The sight tube 22 itselfcould be made of PFA tetrafluoroethylene. External components could bemade of polyvinylchloride. In embodiments wherein it is desired that thefloat 72 be heavier, a polytetrafluorethylene float 72 could be embeddedwith stainless steel or be replaced by a completely stainless steelfloat. Consequently the whole flow meter assembly could be madeinsoluble and impervious to chemical action with a liquid.

Numerous characteristics and advantages of the invention have been setforth in the foregoing description. It will be understood, of course,that this disclosure is, in many respects, only illustrative. Changescan be made in details, particularly in matters of shape, size, andarrangement of parts without exceeding the scope of the invention. Theinvention's scope is defined in the language in which the appendedclaims are expressed.

What is claimed is:
 1. A fluid flow controller and meter, comprising:(a)a metering tube having a passage formed axially therethrough, and aslit-like orifice, having a length axially disposed, intersecting saidpassage along the length thereof, a portion of said passage on one sideof said orifice defining a flow duct, and a portion of said passage on asecond side of said orifice defining a valve-receiving duct; (b) aconduit having a bore formed axially therethrough, said conduit borebeing in fluid communication with said metering tube passage flow ductthrough said orifice when said orifice is unobstructed, said conduitincluding means for measuring a volumetric flow of a fluid through saidfluid flow controller and meter; and (c) a valve member having agenerally planar forward end, substantially orthogonal to an axis ofsaid passage, disposed in said passage for selective positioning axiallytherealong and retraction across said orifice in a direction away fromsaid flow duct to regulate fluid flow through said bore, wherein as saidvalve member is retracted increased fluid flow is permitted through saidconduit bore as a greater proportion of said orifice is opened to saidflow duct.
 2. A fluid flow controller and meter in accordance with claim1 wherein said means for measuring a volumetric flow of a fluid throughsaid fluid flow meter includes;(a) a sight tube having a sight tube boreformed axially therethrough in fluid communication with said conduitbore; and (b) a flow sensitive element disposed for axial movementthrough said sight tube bore and biased away from said metering tubewherein the size and spatial relationship of said flow sensitive elementbeing such, relative to said bore, so that as said element approaches anend of said sight tube bore proximate said orifice, an increasinglygreater volume of fluid flow is permitted through said bore around saidelement; and (c) means for ascertaining volumetric flow of fluid throughthe flow controller and meter depending upon the axial position of theflow sensitive element.
 3. A flow controller and meter in accordancewith claim 1 wherein an axis with respect to which said passage isformed is oriented generally horizontally, and wherein an axis withrespect to which said bore is formed is oriented generally vertically.4. A flow controller and meter in accordance with claim 2 wherein adiametrical dimension of said sight tube bore tapers radially outwardlyas said bore approaches said orifice, a flow determinant diametricaldimension of said flow sensitive element remaining constant.
 5. A flowcontroller and meter in accordance with claim 2 wherein said flowsensitive element is gravity-biased away from said metering tube.
 6. Aflow controller and meter in accordance with claim 2 further comprisingmeans for maintaining said flow sensitive element coaxial with respectto said bore.
 7. A flow controller and meter in accordance with claim 6wherein an aperture is formed centrally within said flow sensitiveelement, and wherein said coaxial maintaining means comprises a rod,aligned along the axis of said bore, passing through said apertureformed centrally within said flow sensitive element.
 8. A flowcontroller and meter in accordance with claim 1 wherein saidascertaining means comprises a series of graduated indicia along saidsight tube, each indicium being representative of a particular fluidflow value.
 9. A flow controller and meter in accordance with claim 2wherein said metering tube, said sight tube, said flow sensitiveelement, and said valve member are formed of a material insoluble tocorrosive acids, bases and solvents and deionized water.
 10. A flowcontroller and meter in accordance with claim 9 wherein said flowsensitive element is formed from polytetrafluoro-ethylene.
 11. A fluidflow controller and meter, comprising:(a) a metering tube having apassage formed axially therethrough, and a slit-like orifice, having alength axially disposed, intersecting said passage along the lengththereof, a portion of said passage on one side of said orifice defininga flow duct, and a portion of said passage on a second side of saidorifice defining a valve-receiving duct; (b) a sight tube having a boreformed axially therethrough, said bore being in fluid communication withsaid metering tube passage flow duct through said orifice when saidorifice is unobstructed, said sight tube further including a flowsensitive element disposed for axial movement through said bore andbiased away from said metering tube, the size and spatial relationshipof said flow sensitive element being such, relative to said bore, sothat, as said element approaches an end of said bore proximate saidorifice, an increasingly greater volume of fluid flow is permittedthrough said bore around said element; (c) a valve member, having agenerally planar forward end substantially orthogonal to an axis of saidpassage, disposed in said passage for selective positioning axiallytherealong, and retractive across said orifice in a direction away fromsaid flow duct to regulate fluid flow through said flow duct to regulatefluid flow through said bore, wherein, as said valve member ispositioned to permit increased fluid flow through said bore, said flowsensitive element is urged by the fluid flow toward said end of saidbore proximate said orifice; and (d) means for ascertaining volumetricflow of fluid through the flow meter depending upon the axial positionof the flow sensitive element attained within said bore.
 12. A flowcontroller and meter in accordance with claim 11 wherein a diametricaldimension of said bore tapers radially outwardly as said bore approachessaid orifice, a flow determinant diametrical dimension of said flowsensitive element remaining constant.
 13. A flow controller and meter inaccordance with claim 11 wherein an axis with respect to which saidpassage is formed is oriented generally horizontally, and wherein anaxis with respect to which said bore is formed is oriented generallyvertically.
 14. A flow controller and meter in accordance with claim 13wherein said flow sensitive element is gravity-biased away from saidmetering tube.
 15. A flow controller and meter in accordance with claim14 further comprising means for maintaining said flow sensitive elementcoaxial with respect to said bore.
 16. A flow controller and meter inaccordance with claim 15 wherein an aperture is formed centrally withinsaid flow sensitive element, and wherein said coaxial maintaining meanscomprises a rod, aligned along the axis of said bore, passing throughsaid aperture formed centrally within said flow sensitive element.
 17. Aflow controller and meter in accordance with claim 11 wherein saidascertaining means comprises a series of graduated indicia along saidsight tube, each indicium being representative of a particular fluidflow value.
 18. A flow controller and meter in accordance with claim 11wherein said metering tube, said sight tube, said flow sensitiveelement, and said valve member are formed of a material insoluble tocorrosive acids and solvents and deionized water.
 19. A flow controllerand meter in accordance with claim 18 wherein said flow sensitiveelement is formed from polytetrafluoro-ethylene.
 20. A flow controllerand meter in accordance with claim 18 wherein said flow sensitiveelement is formed from a combination of polytetrafluorethylene andstainless steel.